SLO and Error-Budget Suite
An exact reliability mathematics suite for experienced SRE and platform teams. It converts an SLO into time and event budgets, measures the observed SLI and calculates consumption and burn without floating-point approximation.
Who this Lab is for
Designed for
- Senior SRE and platform engineers
- Service owners reviewing SLI telemetry
- Engineering leaders operating an established error-budget policy
Use it when
- Checking monitoring-system calculations independently
- Quantifying incident impact against an event-based SLO
- Reviewing remaining budget before a change window
- Translating availability targets into exact time allowances
A complete run, step by step
Enter the approved target
Use the target from the reviewed SLO specification, with up to six decimal places.
Define the compliance window
Enter the number of complete 24-hour days used by the reporting period.
Supply event counts
Use the SLI denominator after exclusions and the bad-event numerator from the same query.
Reconcile the result
Compare allowance, actual SLI, burn rate and multiwindow alert thresholds with the monitoring implementation.
What you will need
Prepare the following information before starting. Use measured evidence where possible; defaults are examples and should not be treated as recommendations.
SLO target
Decimal percentage with up to six fractional digits. Must be below 100%.
Compliance window
Number of complete 24-hour days in the SLO window.
Total valid events
Denominator after applying the SLI's documented validity criteria.
Bad events
Valid events that failed the SLI's good-event criteria.
What the result tells you
Your report includes
- Floor-rounded time allowance in milliseconds and a readable duration
- Floor-rounded event budget and remaining failures
- Observed event SLI, budget consumption and burn rate
- Exact fast-page, medium-page and slow-ticket multiwindow thresholds
- Visible formulae and versioned calculation contract
How it is determined
The engine converts the percentage into a scaled integer, then uses BigInt rational arithmetic. Error budget is 100% minus the SLO. Allowed bad events are floor(total valid events multiplied by the error-budget fraction). Burn rate is the observed bad-event ratio divided by that fraction.
All arithmetic uses integers and explicit rational rounding. The result is exact for the supplied SLI counts, SLO target and window; choosing the correct SLI remains the user's responsibility.
Model assumptions
- • Total events already exclude events declared invalid by the SLI specification.
- • Bad events use exactly the same criteria as the approved SLI.
- • A day is defined as 86,400,000 milliseconds for allowance arithmetic.
Three million events at 99.9%
Situation
A 30-day SLO window contains 3,000,000 valid events and 1,250 bad events.
Result
The exact event budget is 3,000 bad events. The observed SLI is 99.958333%, 1,750 events remain and the burn rate is 0.4167×.
Use the result with engineering judgement
- The calculator cannot decide which events belong in an SLI.
- A mathematically correct result can still be operationally misleading if numerator and denominator queries use different filters.
- A day is explicitly defined as 86,400,000 milliseconds; calendar-month and daylight-saving semantics are outside the contract.
Questions before you begin
Why not use ordinary JavaScript numbers?
Event counts and percentage arithmetic use integers and rational rounding so large counts do not silently lose precision.
Does this recommend an SLO target?
No. Target selection is a product and engineering decision. The tool only calculates consequences of the supplied target.
Can this replace monitoring?
No. It is an independent calculation and reconciliation utility for telemetry produced elsewhere.
Ready to run SLO Budget Suite?
Log in to open the full interactive workspace. Your completed result can be saved, revisited and exported as a private report.
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